In many industries, slip and fall accidents represent the highest or second highest type of workers compensation claims. Indeed, slip and fall accidents account for nearly 11 percent of all workers compensation claims as well as 13 percent of all costs related to claims. In some circumstances, it is possible to minimize accidents though rigorous cleaning and inspection protocols, through the inclusion of certain flooring surfaces, or other programs inclined to limit falls, however, the use of proper footwear can also have an impact in limiting falls. Accordingly, slip resistant shoes and soles provide a useful tool for employers and employees to help limit injuries in the workplace.
In the United States, there are no current legal standards for measuring slip resistance of footwear and manufacturers typically use the standards of non-governmental organizations such as the International Organization for Standards (ISO) and the American Society for Testing and Materials (ASTM). Some manufacturers use the Brungaber Mark II (PIAST) slip tester and utilize standards issued by organizations such as the ISO. See ISO 13287-2006 “Personal Protective Equipment-Footwear-Test Method for Slip Resistance, ISO, Geneva, Switzerland.”
Regardless of what standard is used, one type of footwear may test best under certain conditions, but fail under other conditions. For example, shoes and soles designed for use on icy surfaces may not necessarily be as well suited for hard surfaces having liquid spills, or oil, or dust, among other possible materials that increases the chance for slipping. Similarly, the actual tested conditions, including temperature, humidity, and pressure, can all impact results of slip resistance.
In seeking to manufacture a slip resistant sole, it is generally recommended to maximize contact with the walkway surface by pushing or squeezing water and contaminants away from the sole at the heel strike, mid stance and toe-off phases of the gait cycle. See Shoe and Allied Trade Association (SATRA). Wilson, M., Development of SATRA Slip Test and Tread Pattern Design Guidelines, In STP 1103, Slips, Stumbles and Falls: Pedestrian Footwear and Surfaces, B. Everett Gray editor, ASTM International, 100 Barr Harbor Dr. W. Conshohocken, Pa. Maximizing contact with the surface provides for more surface area for friction between the shoe sole and the surface, so as to prevent falls.
Furthermore, the sole or tread material may also impact the slip resistance of the shoe or sole. Shoe manufacturers typically use styrene butadiene rubber (SBR) or nitrile-butadiene rubber (NBR), as well as a number of polyurethane materials for the sole of the footwear. The spectrum of materials includes soft to hard materials. Typically, soft materials offer improved traction but limited durability. Harder materials, while providing for improved durability, typically have reduced traction when compared to softer materials. On icy surfaces, a different material may be appropriate, as rubber alone is often insufficient, and studded soles may be necessary for proper traction and slip resistance. See “Loss Control Reference Note: Preventing Slips and Falls: Slip Resistant Footwear,” Liberty Mutual Group, LC 5407 R2, September 2009.
The prior art has attempted to provide a shoe sole having slip resistant properties, see. e.g.: EP 1762151, WO 2000004802, WO 1999022614, CA 1260704, US D674585, EP 0383489, EP 0367297, US 20130008059, EP 2449906, U.S. Pat. No. 4,724,624, and US 20090188132, yet each of designs have various limitations that preclude their use in one or more situations.
Accordingly, there is a need for an improved shoe comprising slip resistant soles.